Steerable electronic microwave antennae have been used currently since many years.
Antennae of this type currently make use of a plurality of radiating elements arranged in an array of radiating elements the microwave input signal of which is amplitude and phase controlled, so as to finally control the direction of maximum transmission of the antenna.
Such a type of antenna is most difficult to design and to operate accurately, owing to its huge number of radiating elements and amplitude and phase controlling elements, which are necessary to make such a type of antenna operative.
More recently, many attempts have been made to embodying electronic microwave antennas in a much simpler way by using passive electronic elements arranged in an array of passive elements, each of these elements being adapted to radiate microwave in phase relationship.
US patent 2004/022 767 discloses a steerable antenna using an array of metallic patches on a substrate, with these patches being connected to the substrate thanks to metallic bored through holes and connected to each other by variable capacity diodes. Such an antenna makes use of surface waves which operate a radiating element laid above the substrate so as to radiate corresponding microwaves.
US patent 2007/0182639 discloses a tunable impedance surface and a fabricating method thereof. Such a surface operates substantially as a spatial filter.
US patent 2006/0114170 also discloses a tunable frequency selective surface using an array of variable capacity diodes interconnecting metallic wires. Such a surface operates also as a spatial filter adapted to filtering electromagnetic waves.